1. Field of the Present Invention
This invention relates to an electronic component, and an electronic component module, including a MEMS (Micro-Electrical Mechanical System) which is a micro device having an electric function and a mechanical function, and to a method of manufacturing the electronic component.
2. Description of the Related Art
An electronic component having a micro electrical mechanical element has been developed. (Hereinafter, the electronic components and the micro electrical mechanical element are referred to as “MEMS electronic components” and a “MEMS element” respectively.) There have been recent active studies of the MEMS electronic components that use a manufacturing process of Si chips where integrated electric circuits are formed. Generally, the MEMS element has a movable portion since the device involves a mechanical movement. When forming the MEMS element on a semiconductor substrate, such as a Si chip, therefore, it is necessary to form a space for motion around the movable portion of the MEMS element so as to not hinder the mechanical movement.
Two processes of manufacturing a MEMS element have been known. One is a method of forming a sacrifice layer such as a poly silicon, a silicon oxide, metal, and an organic layer on a Si substrate, and forming the movable space in the sacrifice layer. This process is referred to as a “Surface MEMS process.” Another process is referred to as a “bulk (Bulk) MEMS process” in which the movable space is formed in the Si substrate itself.
With regard to the “Surface MEMS process,” after forming the MEMS element on the sacrifice layer, the sacrifice layer in a region corresponding to the movable portion of the MEMS element is removed by etching to form the space for movement. In this process, since the size of the space for movement of the MEMS element is restricted by the thickness of the sacrifice layer, there is little freedom for the design. On the other hand, in the “Bulk MEMS process”, since the Si substrate in the region corresponding to the movable portion is removed from a lower surface of the Si substrate by etching to make a cavity after forming the MEMS element on the Si substrate, a larger space for movement for the MEMS can be prepared.
However, when etching a single crystal Si substrate, the etching rate differs depending on crystal planes thereof. When etching a generally-used Si substrate having a crystal face of (100), a cavity with an etching slope at an angle of 54.7 degrees to the surface of the substrate (i.e., a surface of the slope has a crystal face (111)) will be formed. For this reason, in order to form an opening with a predetermined size in an upper surface (or a main surface) of the substrate, it is inevitable that a considerably large opening is formed in the lower surface of the substrate. Consequently, with regard to the “Bulk MEMS process” where the Si substrate is etched from the lower surface thereof, it is difficult to form the opening in a predetermined size in a predetermined position in the upper surface of the substrate accurately. In addition, since a cavity larger than necessary is formed in the Si substrate, it is difficult to keep the mechanical strength of the Si substrate.
Further, in conventional electronic component modules having the MEMS element, wire bonding is generally used as a lead line for mounting a chip on a printed circuit board. However, when using a component called an RF-MEMS, which is used in the communication field (a switch, a filter, a variable inductor, a variable capacity, an antenna, etc.), there are cases where a parasitic capacitance and inductance are caused by the wire bonding and thus the intended performance cannot be attained.
Furthermore, when packaging the MEMS electronic component, it is necessary to provide a movable space above the MEMS element additionally. Thus, unlike conventional general-purpose packages, resin molding cannot be performed. Consequently, a process of mounting ceramic-packages, wherein an expensive hermetic sealing is performed and which is different from processes of mounting components, such as other circuit chips including LSI, etc., is mainly used. Because of the inconsistency between the mounting processes, it is difficult to manufacture an SIP (System In Package), wherein an MEMS element and other circuit chips are integrated in one package, and thus the MEMS element is usually mounted on a board as an isolated device.